Frequency and/or phase compensated microelectromechanical oscillator

ABSTRACT

Example embodiments of the present invention are directed to a compensated microelectromechanical oscillator, having a microelectromechanical resonator that generates an output signal and frequency adjustment circuitry, coupled to the microelectromechanical resonator to receive the output signal of the microelectromechanical resonator and, in response to a set of values, to generate an output signal having second frequency. The values may be determined using the frequency of the output signal of the microelectromechanical resonator, which depends on the operating temperature of the microelectromechanical resonator and/or manufacturing variations of the microelectromechanical resonator. The frequency adjustment circuitry may include frequency multiplier circuitry, for example, PLLs, DLLs, digital/frequency synthesizers and/or FLLs, as well as any combinations and permutations thereof. The frequency adjustment circuitry, in addition or in lieu thereof, may include frequency divider circuitry, for example, DLLs, digital/frequency synthesizers (for example, DDS) and/or FLLs, as well as any combinations and permutations thereof.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of and claims priority under 35U.S.C. §120 to U.S. patent application Ser. No. 11/982,084, filed onOct. 31, 2007 now U.S. Pat. No. 7,532,081; which is a continuation ofSer. No. 11/796,990, filed on Apr. 30, 2007, now U.S. Pat. No.7,453,324; which is a continuation of U.S. patent application Ser. No.11/240,010, filed on Sep. 30, 2005, now U.S. Pat. No. 7,221,230; whichis a continuation of U.S. patent application Ser. No. 10/754,985, filedon Jan. 9, 2004, now U.S. Pat. No. 6,995,622; all of which areincorporated herein by reference in their entirety.

DESCRIPTION

This invention relates to microelectromechanical systems and techniquesincluding microelectromechanical resonators; and more particularly, inone aspect, to a system and technique for providing a stable andcontrollable microelectromechanical oscillator output frequency that iscontrollable in fine and coarse increments.

Microelectromechanical systems (“MEMS”), for example, gyroscopes,resonators and accelerometers, utilize micromachining techniques (i.e.,lithographic and other precision fabrication techniques) to reducemechanical components to a scale that is generally comparable tomicroelectronics. MEMS typically include a mechanical structurefabricated from or with, for example, a silicon layer usingmicromachining techniques. The silicon layer is disposed on, forexample, an insulation layer that, among other things, serves as asacrificial layer for the MEMS. As such, significant portions of theinsulation layer are etched or removed in order to release themechanical structure. (See, for example, U.S. Pat. Nos. 6,450,029 and6,240,782). In this way, the mechanical structure may function, forexample, as a resonator to provide an output signal having a givenfrequency. A MEMS oscillator typically includes a MEMS resonantstructure and associated drive circuit. (See, for example, U.S. Pat. No.6,577,040, and U.S. Patent Applications 2002/002/021054 and2002/0068370). The frequency of the output signal of the MEMS oscillatoris generally determined during fabrication but may be adjustedthereafter to a precise value using well-known techniques. The MEMSoscillator is designed to provide the desired frequency of the outputsignal over or across an operating temperature. In that way, the MEMSoscillator may be useful in a number of applications in which theenvironment changes over time within a given range.

Many applications of MEMS oscillators require a high frequency resonatorthat is highly controllable and accurate over a wide operatingtemperature. For example, high frequencies can improve oscillator signalto noise ratio. However, such a resonator tends to make frequencyadjustment, stability and control of the oscillator difficult,complicated and expensive. (See, for example, U.S. Pat. Nos. 6,577,040;6,624,726; and U.S. Patent Applications 2003/0089394, 2003/0160539,2003/0168929 and 2003/0173864). A conventional approach to control andadjust the output frequency of the MEMS resonant structure is anapplication of an electrostatic bias between the resonant structure andcontrol electrodes. By increasing the field strength across the gapbetween the resonant structure and control electrodes, the frequency ofthe output signal of the resonant structure may be deceased.

Typically, the minimum required frequency control is determined by theinitial frequency error and the temperature variation of the resonatestructure. As the resonator structure is designed for higherfrequencies, the electric field available across the gap between theresonant structure and control electrodes should normally be increasedto maintain an appropriate range of frequency control. This may beaccomplished by reducing the width of the gap and/or increasing theavailable voltage to apply across the gap.

In order to achieve high frequencies of the output signal, the necessarygap and voltages tend to complicate the MEMS design, significantlyincrease the cost and difficulty of manufacture of the resonantstructure, and/or require costly control circuitry (for example,high-voltage CMOS circuitry). Notably, an alternative to control andadjust the frequency (which applies as well at high frequencies) is tocontrol temperature of the resonator structure. (See, for example, U.S.Patent Applications 2003/0160539 and 2003/0173864). In this regard, thetemperature of the resonator structure may be controlled to provide amore precise high frequency output. While this technique may offerprecision and/or control, the design of the MEMS resonant structure isconsiderably more complicated. In addition, such a MEMS design oftenrequires additional power as well as temperature adjustment circuitry tocontrol the temperature of the resonant structure. As such, thisalternative may not be suitable for many applications.

There is a need for, among other things, an oscillator employing a MEMSresonator (hereinafter, a “MEMS oscillator”) that overcomes one, some orall of the shortcomings of the conventional systems, designs andtechniques. In this regard, there is a need for an improved MEMSoscillator that provides an output signal that is highly controllable,precise and/or capable of operating over a wide operating temperaturethat overcomes the cost, design, operation and/or manufacturingshortcomings of conventional MEMS oscillator/resonator systems.Moreover, there is a need for an improved MEMS oscillator providing anoutput signal (or output signals, each) having a frequency and/or phasethat is accurate, stable, controllable, programmable, definable and/orselectable before and/or after design, fabrication, packaging and/orimplementation.

SUMMARY OF THE INVENTION

There are many inventions described and illustrated herein. In a firstprincipal aspect, the present invention is directed to a compensatedmicroelectromechanical oscillator, having a microelectromechanicalresonator that generates an output signal and frequency adjustmentcircuitry, coupled to the microelectromechanical resonator to receivethe output signal of the microelectromechanical resonator and, inresponse to a set of values, to generate an output signal having secondfrequency. In one embodiment, the values may be determined using thefrequency of the output signal of the microelectromechanical resonator,which depends on the operating temperature of the microelectromechanicalresonator and/or manufacturing variations of the microelectromechanicalresonator. In one embodiment, the frequency adjustment circuitry mayinclude frequency multiplier circuitry, for example, PLLs, DLLs,digital/frequency synthesizers and/or FLLs, as well as any combinationsand permutations thereof. The frequency adjustment circuitry, inaddition or in lieu thereof, may include frequency divider circuitry,for example, DLLs, digital/frequency synthesizers (for example, DDS)and/or FLLs, as well as any combinations and permutations thereof. Themicroelectromechanical resonator may be compensated (partially or fully)or uncompensated. In one embodiment, the values employed by thefrequency adjustment circuitry may be dynamically determined based on anestimation of the temperature of the microelectromechanical resonator.These values may be determined using empirical data and/or mathematicalmodeling. Moreover, in one embodiment, the values are determined usingdata which is representative of the operating temperature of themicroelectromechanical resonator.

In one embodiment, the frequency adjustment circuitry may includefrequency multiplier circuitry (for example, fractional-N PLL or digitalsynthesizer). In another embodiment, the frequency adjustment circuitryincludes (1) frequency multiplier circuitry and (2) frequency dividercircuitry. The frequency multiplier circuitry (for example, fractional-NPLL) generates an output signal having frequency using a first set ofvalues and the output signal of the microelectromechanical resonator,wherein the frequency of the output signal is greater than the frequencyof the microelectromechanical resonator. The frequency divider circuitry(for example, integer-N PLL, a DLL, or a DDS) is coupled to thefrequency multiplier circuitry to receive the output signal of thefrequency multiplier circuitry and, based on a second set of values,generates the output signal having the second frequency. In yet anotherembodiment, the frequency adjustment circuitry includes (1) a firstfrequency multiplier circuitry (for example, fractional-N PLL ordigital/frequency synthesizer) and (2) a second frequency multipliercircuitry (for example, integer-N PLL or digital/frequency synthesizer).

In another principal aspect, the present invention is directed to acompensated microelectromechanical oscillator, having amicroelectromechanical resonator (compensated (partially or fully) oruncompensated) that generates an output signal. The compensatedmicroelectromechanical oscillator also includes frequency adjustmentcircuitry, coupled to the microelectromechanical resonator to receivethe output signal of the microelectromechanical resonator and, inresponse to a set of values, to generate an output signal having anoutput frequency. In one embodiment, the set of values is determinedbased on the frequency of the output signal of themicroelectromechanical resonator and data which is representative of theoperating temperature of the microelectromechanical resonator.

In one embodiment, the values are dynamically provided to the frequencyadjustment circuitry. In another embodiment, the values are determinedusing an estimated frequency of the output signal of themicroelectromechanical resonator and wherein the estimated frequency isdetermined using empirical data. In yet another embodiment, the valuesare determined using an estimated frequency of the output signal of themicroelectromechanical resonator and wherein the estimated frequency isdetermined using mathematical modeling.

In one embodiment, the frequency adjustment circuitry may includefrequency multiplier circuitry (for example, fractional-N PLL or digitalsynthesizer).

In another embodiment, the frequency adjustment circuitry includes (1)frequency multiplier circuitry and (2) frequency divider circuitry. Thefrequency multiplier circuitry (for example, fractional-N PLL) generatesan output signal having frequency using a first set of values and theoutput signal of the microelectromechanical resonator, wherein thefrequency of the output signal is greater than the frequency of themicroelectromechanical resonator. The frequency divider circuitry (forexample, integer-N PLL, a DLL, or a DDS) is coupled to the frequencymultiplier circuitry to receive the output signal of the frequencymultiplier circuitry and, based on a second set of values, generates theoutput signal having the second frequency.

In yet another embodiment, the frequency adjustment circuitry includes(1) a first frequency multiplier circuitry (for example, fractional-NPLL or digital/frequency synthesizer) and (2) a second frequencymultiplier circuitry (for example, integer-N PLL or digital/frequencysynthesizer).

In another principal aspect, the present invention is a method ofprogramming a temperature compensated microelectromechanical oscillatorhaving a microelectromechanical resonator. The resonator generates anoutput signal wherein the output signal includes a first frequency. Themicroelectromechanical oscillator further includes frequency adjustmentcircuitry, coupled to the resonator to receive the output signal of themicroelectromechanical resonator and to provide an output signal havinga frequency that is within a predetermined range of frequencies. Themethod of this aspect of the invention comprises (1) measuring the firstfrequency of the output signal of the microelectromechanical resonatorwhen the microelectromechanical resonator is at a first operatingtemperature, (2) calculating a first set of values, and (3) providingthe first set of values to the frequency adjustment circuitry.

In one embodiment, the method further includes calculating a second setof values wherein the frequency adjustment circuitry, in response to thesecond set of values, provides the output signal having the frequencythat is within a predetermined range of frequencies when themicroelectromechanical resonator is at a second operating temperature.The second set of values may be calculated using empirical data or usingmathematical modeling.

In yet another principal aspect, the present invention is a method ofoperating a temperature compensated microelectromechanical oscillatorhaving a microelectromechanical resonator and frequency adjustmentcircuitry. The resonator is employed to generate an output signalwherein the output signal includes a first frequency. The frequencyadjustment circuitry is coupled to the resonator to receive the outputsignal of the microelectromechanical resonator and, in response to afirst set of values, provides an output signal having a second frequencywherein the second frequency is within a predetermined range offrequencies. The method of this aspect of the invention includes (1)acquiring data which is representative of the temperature of themicroelectromechanical resonator; (2) determining that themicroelectromechanical resonator is at a second operating temperature;(3) determining a second set of values wherein the frequency adjustmentcircuitry, in response to the second set of values, provides the outputsignal having the frequency that is within a predetermined range offrequencies when the microelectromechanical resonator is at the secondoperating temperature; and (4) providing the second set of values to thefrequency adjustment circuitry. The second set of values may becalculated using empirical data or using mathematical modeling.

In one embodiment, the method further includes measuring the temperatureof the microelectromechanical resonator and calculating the operatingtemperature of the microelectromechanical resonator.

In another embodiment, the second set of values includes the first andsecond subsets of values and the frequency adjustment circuitryincludes: (1) first frequency multiplier circuitry (for example,fractional-N PLL) to generate an output signal having frequency using afirst subset of values wherein the frequency of the output signal isgreater than the first frequency; and (2) second frequency multipliercircuitry (for example, an integer-N PLL or a digital/frequencysynthesizer), coupled to the first frequency multiplier circuitry, toreceive the output signal of the first frequency multiplier circuitryand, based on a second subset of values, to generate the output signalhaving the second frequency wherein the second frequency is greater thanthe frequency of the output signal of the first frequency multipliercircuitry. The method further comprises determining the first subset ofvalues wherein the frequency adjustment circuitry, in response to thefirst subset of values, provides the output signal having the frequencythat is within a predetermined range of frequencies when themicroelectromechanical resonator is at the second operating temperature.

Again, there are many inventions described and illustrated herein. ThisSummary of the Invention is not exhaustive of the scope of the presentinvention. Moreover, this Summary is not intended to be limiting of theinvention and should not be interpreted in that manner. While certainembodiments, features, attributes and advantages of the inventions havebeen described in this Summary of the Invention, it should be understoodthat many others, as well as different and/or similar embodiments,features, attributes and/or advantages of the present inventions, whichare apparent from the description, illustrations and claims, whichfollow.

BRIEF DESCRIPTION OF THE DRAWINGS

In the course of the detailed description to follow, reference will bemade to the attached drawings. These drawings show different aspects ofthe present invention and, where appropriate, reference numeralsillustrating like structures, components, materials and/or elements indifferent figures are labeled similarly. It is understood that variouscombinations of the structures, components, materials and/or elements,other than those specifically shown, are contemplated and are within thescope of the present invention.

FIG. 1 is a block diagram representation of a conventional MEMSoscillator;

FIGS. 2A-2E are block diagram representations of a frequency and/orphase compensated MEMS oscillator in accordance with certain aspects ofthe present inventions;

FIGS. 3A-3H are block diagram representations of a conventional phaselocked loop, delay locked loop, direct digital synthesizer, andfractional synthesizer;

FIGS. 4A-4C, 5A-5C, 6A-6C, 7A-7C and 8A-8C generally illustrate typicalcharacteristics of an output signal of MEMS oscillator versustemperature, various exemplary operations or functions of thecompensation circuitry versus temperature, and certain characteristicsof the output signal of compensated MEMS oscillator over temperatureand/or initial error;

FIGS. 9A-9D illustrate more detailed block diagrams of the frequencyand/or phase compensated MEMS oscillators in accordance with certainaspects of the present inventions;

FIGS. 10A-10D illustrate detailed block diagrams of MEMS oscillators,including frequency divider circuitry, according to certain otheraspects of the present inventions;

FIGS. 11A and 11B illustrate block diagram representations of afrequency and/or phase compensated MEMS oscillator including a pluralityof output signals, according to certain aspects of the presentinvention;

FIGS. 12A and 12B illustrate block diagram representations of afrequency and/or phase compensated MEMS oscillator including a pluralityof output signals, according to certain aspects of the presentinvention;

FIGS. 13A and 13B illustrate block diagram representations of a MEMSoscillator having frequency multiplier circuitry and the frequencydivider circuitry that includes independent frequency and phase controlof a plurality of output signals, in accordance with certain aspects ofthe present invention;

FIGS. 14A-14D illustrate block diagram representations of a MEMSoscillator having frequency multiplier/divider circuitry and secondarymultiplier/divider circuitry, in accordance with certain aspects of thepresent invention;

FIG. 15A illustrates a plan view (i.e., three-dimensional) block diagramrepresentation of the frequency and/or phase compensated MEMS oscillatorintegrated in or on a common substrate, according to certain aspects ofthe present invention;

FIG. 15B illustrates a plan view block diagram representation of thefrequency and/or phase compensated MEMS oscillator, including integratedtemperature sensors, integrated on or in a common substrate, accordingto certain aspects of the present invention;

FIGS. 15C-15F illustrate plan view block diagram representations offrequency and/or phase compensated MEMS oscillators, integrated in or ona common substrate, according to certain aspects of the presentinvention;

FIGS. 16A-16C illustrate plan view block diagram representations ofcompensated MEMS oscillators, wherein MEMS portion and the compensationand control circuitry are disposed on or in separate substrates,according to certain aspects of the present invention;

FIGS. 17A-17C illustrate plan view block diagram representations ofinterconnection techniques of the MEMS oscillators of FIGS. 13C-13F,according to certain aspects of the present invention;

FIGS. 18A-18H illustrate cross-sectional views of a portion of the MEMSoscillator, integrated in or on a common substrate, with a portion ofthe compensation and control circuitry, according to certain aspects ofthe present inventions;

FIGS. 19A-19D illustrate plan view block diagram representations ofcompensated MEMS oscillators, wherein the drive circuitry is disposed onthe substrate of the compensation and control circuitry, according tocertain aspects of the present invention;

FIG. 20 illustrates a plan view block diagram representation of acompensated MEMS oscillators, wherein drive circuitry portion of thecompensated MEMS oscillator is disposed on or in a substrate that isdifferent from the substrates containing the MEMS resonator andcompensation and control circuitry, according to certain aspects of thepresent invention;

FIGS. 21A and 21B are block diagram representations of a frequencyand/or phase compensated MEMS oscillator in accordance with certainaspects of the present inventions;

FIGS. 22A and 22B are block diagram representations of a frequencyand/or phase compensated MEMS oscillator, implemented in conjunctionwith modulation circuitry, in accordance with certain aspects of thepresent inventions; and

FIGS. 23A-23C and 24A-24I illustrate exemplary permutation and/orcombination of the specific clock or signal alignment circuitry that maybe employed for the various topologies of the compensation circuitry.

DETAILED DESCRIPTION

There are many inventions described and illustrated herein. In oneaspect, the present invention is directed to a frequency and/or phasecompensated MEMS oscillator (hereinafter “frequency/phase compensatedMEMS oscillator” or “compensated MEMS oscillator”) for providing ahighly accurate, stable, controllable, programmable, definable and/orselectable output signal(s). In this regard, the controllable,programmable, definable and/or selectable aspect of the output signal(s)may be the frequency and/or phase of the output signal. For example, thepresent invention may provide a highly accurate, stable, controllable,programmable, definable and/or selectable output signal(s) having apredetermined, predefined and/or specific frequency (for example, alower frequency of 1 Hz to 100 kHz, a more moderate frequency of 1-100MHz or a higher frequency of 1-10 GHz) and/or a desired phase (forexample, 0°, 90° and/or 180°). Indeed, the frequency and/or phase of theoutput signal may be adjusted, compensated, controlled, programmed,defined and/or selected before and/or after design, fabrication,packaging and/or implementation within circuitry.

With reference to FIGS. 2A-2E, frequency/phase compensated MEMSoscillator 100 of the present invention employs MEMS resonator 12 anddrive circuit 14 (i.e., MEMS oscillator 10) to provide a temporallyrepeating output signal having a known frequency (for example, a clocksignal). Notably, MEMS resonator 12 and drive circuit 14 may employ anytype of MEMS design and/or control, whether now known or laterdeveloped, including, for example, those discussed above in theBackground of the Invention. Indeed, drive circuit 14 of the presentinvention may or may not include circuitry that controls and/or adjuststhe frequency of the output signal.

The output of MEMS oscillator 10 is provided to compensation and controlcircuitry 16. In one embodiment, compensation and control circuitry 16includes frequency and/or phase compensation circuitry 18 (hereinafter“compensation circuitry 18”), which receives the output of MEMSoscillator 10 and adjusts, compensates, corrects and/or controls thefrequency and/or phase of the output of MEMS oscillator 10. In thisregard, compensation circuitry 18 uses the output of MEMS oscillator 10to provide an adjusted, corrected, compensated and/or controlled outputhaving, for example, a desired, selected and/or predetermined frequencyand/or phase.

The characteristics of the output signal (frequency and/or phase) ofcompensation circuitry 18 may be pre-set, pre-programmed and/orprogrammable to provide an output signal having, for example, a desired,selected and/or predetermined frequency and/or phase. Thecharacteristics of the output signal may be pre-programmed orprogrammable during, for example, fabrication, test, and/or calibration.Indeed, the characteristics of the output signal may also be programmedduring normal operation.

The compensation circuitry 18 may employ one or more phase locked loops(PLLs), delay locked loops (DLLs), digital/frequency synthesizer (forexample, a direct digital synthesizer (“DDS”), frequency synthesizer,fractional synthesizer and/or numerically controlled oscillator) and/orfrequency locked loops (FLLs). In these embodiments, the output of MEMSoscillator 10 is employed as the reference input signal (i.e., thereference clock). The PLL, DLL, digital/frequency synthesizer and/or FLLmay provide frequency multiplication (i.e., increase the frequency ofthe output signal of the MEMS oscillator). The PLL, DLL,digital/frequency synthesizer and/or FLL may also provide frequencydivision (i.e., decrease the frequency of the output signal of the MEMSoscillator). Moreover, the PLL, DLL, digital/frequency synthesizerand/or FLL may also compensate using multiplication and/or division toadjust, correct, compensate and/or control the characteristics (forexample, the frequency, phase and/or jitter) of the output signal of theMEMS resonator. Notably, block diagrams of an embodiment of a typical orconventional PLL and DLL are provided in FIGS. 3A and 3B, respectively;block diagrams of embodiments of typical or conventional DSS areprovided in FIGS. 3C and 3D.

The multiplication or division (and/or phase adjustments) bycompensation circuitry 18 may be in fine or coarse increments. Forexample, compensation circuitry 18 may include an integer PLL, afractional PLL and/or a fine-fractional-N PLL to precisely select,control and/or set the output signal of compensated MEMS oscillator 100.In this regard, the output of MEMS oscillator 10 may be provided to theinput of the fractional-N PLL and/or the fine-fractional-N PLL(hereinafter collectively “fractional-N PLL”), which may be pre-set,pre-programmed and/or programmable to provide an output signal having adesired, selected and/or predetermined frequency and/or phase. Notably,block diagrams of an embodiment of a typical or conventionalfractional-N PLL and fractional synthesizer are provided in FIGS. 3E and3H, respectively; block diagrams of embodiments of typical orconventional fractional-N DLL and are provided in FIGS. 3F and 3G.

Notably, in one embodiment, the parameters, references (for example,frequency and/or phase), values and/or coefficients employed bycompensation circuitry 18 in order to generate and/or provide anadjusted, corrected and/or controlled output having, for example, adesired, selected and/or predetermined frequency and/or phase (i.e., thefunction of compensation circuitry 18), may be externally provided tocompensation circuitry 18 either before or during operation ofcompensated MEMS oscillator 100. In this regard, a user or externalcircuitry/devices/systems may provide information representative of theparameters, references, values and/or coefficients to set, change,enhance and/or optimize the performance of compensation circuitry 18and/or compensated MEMS oscillator 100. With continued reference to FIG.2B, such information may be provided directly to compensation circuitry18 or to memory 20 for use by compensation circuitry 18.

Notably, compensation circuitry 18 may also provide a plurality ofoutputs, each having a desired, selected and/or predetermined relativeor absolute frequency and/or phase. For example, frequency/phasecompensated MEMS oscillator 100 of the present invention may provide anumber of output signals each having a desired, selected and/orpredetermined frequency (for example, one-quarter, one-half and/or twicethe frequency of the output signal of MEMS oscillator 10) as well as adesired, selected and/or predetermined phase relationship relative to areference input and/or the other output signals (for example, 0°, 45°,90° and/or 180°). Indeed, the frequency and/or phase relationship may beprogrammable during, for example, fabrication, test, calibration and/orduring normal operation. Notably, the plurality of outputs may begenerated by the same or separate or different compensation circuitry18.

With reference to FIGS. 2C-2E, in certain embodiments, compensated MEMSoscillator 100 includes control circuitry 22 to control compensationcircuitry 18. In this regard, control circuitry 22, in one embodiment,may provide, calculate and/or determine (based on external inputs and/ordata resident in local and/or resident/integrated memory 20 that may be,for example, programmed during fabrication, test, calibration and/ordynamically during operation) the parameters, references, values and/orcoefficients necessary for compensation circuitry 18 (for example,parameters and/or coefficients for a PLL(s), digital/frequencysynthesizer and/or DLL(s)) to adjust, correct and/or control thefrequency and/or phase of the output of MEMS oscillator 10 so that theattributes and/or characteristics (for example, frequency, phase,modulation, spread, jitter, duty cycle, locking/response time, noiserejection and/or noise immunity) of the output signal(s) of compensatedMEMS oscillator 100 are suitable, desired and/or within predetermined orpre-selected limits (for example, within 25 ppm of a desired, suitableand/or predetermined frequency, and 1% of a desired, suitable and/orpredetermined phase and/or duty cycle).

Thus, in one embodiment, the parameters, references (for example,frequency and/or phase), values and/or coefficients employed by controlcircuitry 22 to set and/or control compensation circuitry 18 may beexternally provided to control circuitry 22 either before or duringoperation of compensated MEMS oscillator 100. In this regard, a user orexternal circuitry/devices/systems may provide informationrepresentative of the parameters, references, values and/or coefficientsin order to set, change, enhance and/or optimize the performance ofcompensation circuitry 18 and/or compensated MEMS oscillator 100. Suchinformation may be provided directly to control circuitry 22 or tomemory 20 to be used by control circuitry 22.

In another embodiment, the parameters, references, values and/orcoefficients employed by control circuitry 22 to set, program and/orcontrol compensation circuitry 18 may be pre-programmed or pre-set, forexample, by permanently, semi-permanently or temporarily (i.e., untilre-programmed) storing information which is representative of theparameters, references, values and/or coefficients in memory 20 such asSRAM, DRAM, ROM, PROM, EPROM, EEPROM or the like (e.g., configuring thestate of a certain pin or pins on the package). In this embodiment ofthe present invention, the information representative of the parameters,references, values and/or coefficients may be stored in, for example, anSRAM, DRAM, ROM or EEPROM. The information which is representative ofthe parameters, references, values and/or coefficients may be stored orprogrammed in memory 20 during fabrication, test, calibration and/oroperation. In this way, control circuitry 22 may access memory 20 toretrieve the necessary information during start-up/power-up,initialization, re-initialization and/or during normal operation offrequency/phase compensated MEMS oscillator 100.

It should be noted that memory 20 may be comprised of discretecomponent(s) or may reside on or in the integrated circuit containingcompensation circuitry 18, control circuitry 22 and/or frequency/phasecompensated MEMS oscillator 100.

Notably, control circuitry 22 may also control the operation of MEMSoscillator 10. (See, for example, FIGS. 2D and 2E). For example, controlcircuitry 22 may control the operation of MEMS resonator 12 (directly)and/or drive circuit 14 which, in turn, adjusts the operation and/orperformance of MEMS resonator 12. In this way, the output signal of MEMSoscillator 10 may be adjusted, corrected and/or controlled to provide asignal having a frequency within a given, predetermined and/or desiredrange (for example, 1-100 MHz.+−.10 ppm). All techniques for controllingthe operation of MEMS oscillator 10, whether now known or laterdeveloped, are intended to be within the present invention. Theinformation or data used to control the operation of the MEMS oscillatormay be provided externally or may be retained in memory 20, in the samemanner discussed above in connection with the parameters, references,values and/or coefficients employed to control compensation circuitry18.

With reference to FIG. 2E, frequency/phase compensated MEMS oscillator100 of the present invention may also include temperature sensorcircuitry 24. The temperature sensor circuitry 24, in one embodiment,receives data (current or voltage, in analog or digital form) which isrepresentative of the temperature of MEMS oscillator 10 (or portionsthereof and/or compensation circuitry 18 (via temperature sensor(s) 26)from one or more discrete temperature sensors (collectively illustratedas temperature sensors 26 but not individually illustrated). Inresponse, temperature sensor circuitry 24 determines and/or calculatesinformation which is representative of the corresponding operatingtemperature (i.e., the operating temperature of MEMS oscillator 10 (orportions thereof and/or compensation circuitry 18). In this regard, oneor more temperature sensors (for example, from a diode(s), atransistor(s), a resistor(s) or varistor(s)), and/or one or more MEMSstructures may be disposed at selected, significant and/or “critical”locations on the substrate of MEMS oscillator 10 and/or compensationcircuitry 18.

The temperature sensor circuitry 24 provides the information to controlcircuitry 22 which, in response, may determine or calculate newparameters, references, values and/or coefficients (i.e., absoluteinformation), or adjustment to the existing or current parameters,references, values and/or coefficients (i.e., relative information) toaddress and/or compensate for the change in temperature. In this regard,control circuitry 22 may determine and/or calculate the parameters,references (for example, frequency and/or phase), values and/orcoefficients (or adjustments thereto) which are necessary forcompensation circuitry 18 to generate and/or provide the suitable,desired and/or predetermined output signal(s) (for example, signalshaving the desired, suitable and/or predetermined frequency and/orphase).

Indeed, control circuitry 22 may adjust the operation of MEMS oscillator10 in accordance with changes in the operating conditions and/orenvironment of frequency/phase compensated MEMS oscillator 100, or partsthereof (for example, MEMS oscillator 10 and/or compensation circuitry18). For example, in one embodiment, control circuitry 22 may employ thedata from temperature sensor circuitry 24 to control the frequency ofthe output of MEMS oscillator 10 (directly) and/or (indirectly) viadrive circuit 14. In this way, the output signal of MEMS oscillator 10may be adjusted, corrected and/or controlled to accommodate and/orcompensate for changes in the operating conditions and/or environment.The control circuitry 22, in one embodiment, employs a look-up tableand/or a predetermined or mathematical relationship to adjust and/orcontrol the operation of MEMS oscillator 10 to compensate and/or correctfor changes in ambient temperature (i.e., the temperature of MEMSoscillator 10).

In another embodiment, control circuitry 22 may adjust, correct and/orcontrol MEMS oscillator 10 and the performance characteristics ofcompensation circuitry 18 to, for example, provide a signal having afrequency and/or phase within a given, predetermined and/or desiredrange. For example, control circuitry 22 may adjust, correct and/orcontrol the frequency of the output of MEMS oscillator 10, as describedabove. In addition, control circuitry 22 may also determine and/orcalculate new parameters, references, values and/or coefficients (oradjustment to the current parameters, references, values and/orcoefficients) for use by compensation circuitry 18, as a result of theadjustment, correction and/or control of the frequency of the output ofMEMS oscillator 10. In this way, a more optimum performance ofcompensated MEMS oscillator 100 may be obtained given the operatingconditions and/or environment of the MEMS oscillator 10 and/orcompensation circuitry 18.

The output signal MEMS oscillator 10 over temperature, the generalexemplary compensation operations or functions of compensation circuitry18 over temperature, and the output signal of compensated MEMSoscillator 100 over temperature (i.e., having a desired, selected and/orpredetermined frequency and/or phase) are generally illustrated in FIGS.4A-4C, 5A-5C, 6A-6C, 7A-7C and 8A-8C. In this regard, the output signalof compensated MEMS oscillator 100 in each instance includes desired,selected and/or predetermined characteristics (for example, desired,selected and/or predetermined frequency and/or phase) at a given,predetermined and/or particular frequency and/or temperature. The outputsignal of compensated MEMS oscillator 100 in each instance may alsoinclude desired, selected and/or predetermined characteristics for afrequency, over a set or range of frequencies and/or set or range oftemperatures. For example, with reference to FIGS. 4C 5C, and 8C, thefrequency versus temperature of the output signal of compensated MEMS100 is constant or “flat” (or substantially constant or flat) and, assuch, the frequency remains constant (or substantially constant) over arange of temperatures (for example, the operating temperatures ofcompensated MEMS oscillator 100).

Notably, FIGS. 5B and 6B include a more granular frequency compensationby circuitry 18 than that illustrated in FIGS. 4B, 7B, and 8B. Further,the function of compensation circuitry 18 (see, for example, FIGS. 6Band 7B) may be designed to provide a particular output signalcharacteristic that, while not constant or “flat” over temperature (see,for example, FIGS. 6C and 7C), are within a desired and/or predeterminedspecification that is acceptable and/or suitable. In this regard, thefunction of compensation circuitry 18 does not fully or completelycompensate but the amount of “deviation” is or may be within anacceptable, predetermined and/or specified limits. (See, FIGS. 6C and7C).

In addition, with reference to FIG. 5A, the frequency of the outputsignal MEMS oscillator 10 over temperature may have a discontinuousrelationship. In this embodiment, MEMS resonator 10 may be partiallycompensated and/or designed for temperature variations. As such, in theembodiment of FIGS. 5A-5C, MEMS oscillator 10 and compensation circuitry18 each partially compensate and/or contribute to the compensation overa range of temperatures and/or for a predetermined temperature. Thecharacteristics of the output signal of MEMS oscillator 10 overtemperature or a narrow and/or discrete range of temperatures may bedetermined using well-known mathematical modeling techniques (based on,for example, expected or predetermined frequency response overtemperature based on the relationship to a given/particular oscillatordesign and/or material). Those characteristics may also be determinedusing empirical and/or actual data or measurements. The empirical datamay be employed to extrapolate and/or determine a function orrelationship of output frequency versus temperature. The relationshipmay be determined for one, some or all devices. Alternatively, arelationship may be determined for one or more MEMS oscillators 10 andthen employed for all “similar” MEMS oscillators (for example, all MEMSoscillators derived from a given fabrication “lot” or “lots”, i.e.,devices from the same wafer(s)).

The frequency of the output signal of MEMS oscillator 10 depends, tosome extent, on the manufacturing variances of the fabrication processesas well as materials. Accordingly, while MEMS oscillators 10 a, 10 b and10 c may be fabricated using the same techniques, the frequencies mayvary (see, FIG. 8A). Notably, these variations may have a significantimpact when the MEMS oscillators implemented in a given system.

In certain embodiments of the present invention, the “initial” frequencyof the output signal (i.e., fsub.a, fsub.b, fsub.c) of MEMS oscillators10 a, 10 b, and 10 c may be measured and thereafter, the function ofcompensation circuitry 18 may be determined, set and/or programmed (see,FIG. 8B). In this regard, the initial frequency may be the frequency ofMEMS oscillator 10 at a given or particular temperature (for example,room temperature or an anticipated operating temperature). The “initial”frequency of MEMS oscillator 10 may be measured, sampled, sensed beforeand/or after packaging or integration/incorporation. The MEMS oscillator10 may also be calibrated at more than one operating condition (forexample, one temperature).

In these embodiments, the initial frequency of the output signal of MEMSoscillators 10 a, 10 b, and 10 c may be employed to calculate and/ordetermine the parameters, references (for example, frequency and/orphase), values and/or coefficients of compensation circuitry 18 a, 18 b,and 18 c (respectively). In this way, the function of compensationcircuitry 18 a, 18 b and 18 c may differ to address and/or compensatethe particular characteristics of the output signal of MEMS oscillators10 a, 10 b, and 10 c (see, FIG. 8B). As such, MEMS oscillator 100 a, 100b, and 100 c (respectively), regardless of differences of the initialfrequency of the output signal of MEMS oscillators 10 a, 10 b, and 10 c,generate and/or provides an output signal having the desired, selectedand/or predetermined characteristics (for example, desired, selectedand/or predetermined frequency and/or phase) at a given, predeterminedor particular frequency and/or temperature (or range of frequenciesand/or temperatures) (see, FIG. 8C).

Notably, however, in certain embodiments, no calibration of MEMSoscillator 10 is performed and any adjustment to the characteristics ofthe output signal of compensated MEMS 100 (due to the absence ofcalibration of MEMS oscillator 10) may be addressed by compensation andcontrol circuitry 16 (and/or compensation circuitry 18). In thisembodiment, it may be advantageous to employ a topology that provides arange of programmability to account or compensate forvariations/differences in the characteristics of the output signal ofMEMS oscillator 10 (for example, the initial frequency of MEMSoscillator 10).

While FIGS. 4A-4C, 5A-5C, 6A-6C, 7A-7C and 8A-8C illustrate frequencyrelationships, phase relationships are similar and/or mathematicallyrelated to the frequency relationships. Accordingly, such FIGURES implyphase and/or phase relationships may be extracted or determinedtherefrom.

With reference to FIG. 9A, in one embodiment, frequency/phasecompensated MEMS oscillator 100 includes MEMS oscillator 10 andcompensation and control circuitry 16. The output signal of MEMSoscillator 10 is provided to compensation circuitry 18. The MEMSoscillator 10 may include a one or more output signals (on one or moresignal lines) to, for example, provide or transmit a single ended signaland/or a differential signal pair. As such, MEMS oscillator 10 mayprovide one or more signals, including, for example, differentialsignals.

In this embodiment, the output signal of MEMS oscillator 10 is providedas an input to frequency multiplier circuitry 28. The frequencymultiplier circuitry 28 is employed to controllably increase thefrequency of the output of MEMS oscillator 10. For example, thisembodiment of the present invention may be employed to provide a highlycontrollable, programmable, definable, selectable and/or accurate outputsignal having a stable moderate frequency (for example, 1-100 MHz) or astable high frequency (for example, 1-10 GHz).

In one embodiment, frequency multiplier circuitry 28 includes one ormore FLL(s), PLL(s), DLL(s) and/or digital/frequency synthesizers (forexample, numerically controlled oscillators). The frequency multipliercircuitry 28 of this embodiment receive the analog output of MEMSoscillator 10. The FLL(s), PLL(s), DLL(s) and/or digital/frequencysynthesizer(s) may be cascaded in series so that a particular, preciseand/or selectable frequency and phase are obtained. Notably, theoperation and implementation of FLL(s), PLL(s), DLL(s), and/ordigital/frequency synthesizer(s) (for example, DDS(s)) are well known tothose skilled in the art. Any FLL, PLL, DLL and/or digital/frequencysynthesizers, as well as configuration thereof or alternatives therefor,whether now known or later developed, is intended to fall within thescope of the present invention.

Notably, it may be advantageous to employ a fractional-N PLL to generateand/or output a precise and controllable frequency or range offrequencies. Such fractional-N PLLs tend to include a sigma-deltamodulator or divider, or a digital to analog converter ramp. In thisway, frequency multiplier circuitry 28 may be programmed and/orcontrolled to provide a precise frequency or frequency range. Forexample, the fractional-N PLL may be (or similar to) SA8028 or AN10140,both of Philips Semiconductors (The Netherlands), CX72300 from SkyworksSolutions Inc. (Newport Beach, Calif.), and KR-SDS-32, KR-SHDS-32, andKR-SDS45-ST6G all from Kaben Research Inc. (Ontario, Canada). Theseexemplary fractional-N PLLs provide a finely controlled and selectableresolution of the output frequency. Notably, the implementation andoperation of fractional-N PLL(s) are described in detail in applicationnotes, technical/journal articles and data sheets.

Furthermore, it may be advantageous to employ a digital/frequencysynthesizer (for example, a DDS and/or numerically controlledoscillator) to generate and/or output a precise and controllablefrequency or range of frequencies. For example, the digital/frequencysynthesizer may be (or similar to) STEL-1172, STEL-1175 and/orSTEL-1178A, all from Intel Corporation (Santa Clara, Calif.), and/orAD9954 from Analog Devices, Inc. (Norwood, Mass.). All theimplementation and operation of the digital/frequency synthesizers (forexample, DDSs) are described in detail in application notes,technical/journal articles and data sheets.

With continued reference to FIG. 9A, as mentioned above, controlcircuitry 22 may provide, calculate and/or determine the parameters,references, values and/or coefficients necessary for frequencymultiplier circuitry 28 (for example, parameters and/or coefficients forthe fractional-N PLL or DDS) to adjust, correct and/or control thefrequency and/or phase of output signal 30 of compensation circuitry 18.In this way, the output signal(s) on signal line 30 contain and/orpossess suitable, desired, predetermined attributes and/orcharacteristics (for example, frequency, phase, jitter, duty cycle,locking/response time, noise rejection and/or noise immunity). Forexample, where a fractional-N PLL is employed, control circuitry 22 mayprovide the data of the integer value for the pre-divider M and/or thevalues for the fractional divider N to frequency multiplier circuitry 28via data/control signal lines 32.

The control circuitry 22 may include a microprocessor(s) and/orcontroller(s) that is/are appropriately programmed to perform thefunctions and/or operations described herein. For example, in oneembodiment, a microprocessor and/or controller may perform the functionsand/or operations of calculating the parameters, references, valuesand/or coefficients employed by compensation circuitry 18 to generateand/or provide an output signal(s) having accurate, suitable, desiredand/or predetermined characteristics (for example, signals having thedesired, suitable and/or predetermined frequency and/or phase). Allconfigurations and techniques of calculating the parameters, references,values and/or coefficients employed by compensation circuitry 18,whether now known or later developed, are intended to be within thescope of the present invention.

Notably, control circuitry 22 may include a state machine (in lieu of,or, in addition to a microprocessor and/or controller). That is, thefunctions and/or operations described herein may be executed and/orimplemented by a state machine circuitry(s) either alone or incombination with a processor and/or controller. The state machine may befixed, microcoded and/or programmable.

The parameters, references, values and/or coefficients employed bycontrol circuitry 22 to set, program and/or control frequency multipliercircuitry 28 may be externally provided to control circuitry 22 eitherbefore or during operation of compensated MEMS oscillator 100. In thisregard, as mentioned above, a user/operator or externalcircuitry/devices/systems may provide information representative of theparameters, references, values and/or coefficients, via data signallines 34, to set, change, enhance and/or optimize the characteristics ofthe output signal(s) on signal line 30. Such information may be provideddirectly to control circuitry 22 or to memory 20 to be used by controlcircuitry 22.

The parameters, references, values and/or coefficients may also bepre-programmed, for example, by permanently, semi-permanently ortemporarily stored in memory 20. The information may be stored orprogrammed in memory 20 during fabrication, test, calibration and/oroperation. In this way, control circuitry 22 may access memory 20 toretrieve the necessary information during start-up/power-up,initialization, re-initialization and/or during normal operation offrequency multiplier circuitry 28.

With continued reference to FIG. 9A, compensated MEMS oscillator 100 ofthis embodiment further includes temperature sensor circuitry 24. Thetemperature sensor circuitry 24, in one embodiment, receives data(current or voltage, in analog or digital form), on temperature datalines 36, from one or more temperature sensors (not illustrated). Inresponse, temperature sensor circuitry 24 determines and/or calculatesthe operating temperature of MEMS oscillator 10. The temperature sensorcircuitry 24 provides the information to control circuitry 22, viasignal lines 38.

The control circuitry 22, in response, may determine or calculate newparameters, references, values and/or coefficients (i.e., absoluteinformation), or adjustment to the existing or “current” parameters,references, values and/or coefficients (i.e., relative information) toaddress and/or compensate for the change in temperature. In this regard,control circuitry 22 may determine that the calculated operatingtemperature of MEMS oscillator 10 requires adjustment to the existing or“current” parameters, references, values and/or coefficients (i.e.,relative information) to address and/or compensate for the change intemperature. Accordingly, control circuitry 22 may determine orcalculate new parameters, references, values and/or coefficients (i.e.,absolute information), or adjustment to the existing or “current”parameters, references, values and/or coefficients and provide that datato frequency multiplier 28 via data/control signal lines 32.

In addition, or in lieu thereof, control circuitry 22 may adjust theoperation of MEMS oscillator 10 in accordance with changes in theoperating conditions and/or environment of frequency/phase compensatedMEMS oscillator 100, or parts thereof (for example, MEMS oscillator 10and/or compensation circuitry 18). For example, control circuitry 22 mayemploy the data from temperature sensor circuitry 24 to control thefrequency of the output of MEMS oscillator 10 and, in particular, MEMSresonator 10 and/or drive circuit 14, via control line 40. As mentionedabove, by controlling drive circuit 18 the operation and/or performanceof MEMS resonator 12 may be adjusted accordingly. In this way, theoutput signal of MEMS oscillator 10 may be adjusted, corrected and/orcontrolled to accommodate and/or compensate for changes in the operatingconditions and/or environment. The control circuitry 22, in oneembodiment, employs a look-up table and/or a predetermined ormathematical relationship to adjust and/or control the operation of MEMSoscillator 10 to compensate and/or correct for changes in ambienttemperature (i.e., the temperature of MEMS oscillator 10).

Notably, the temperature sensors may be, for example, diode(s),transistor(s), resistor(s) or varistor(s), one or more MEMS structures,and/or other well-known temperature sensing circuits, which are disposedand/or located on or in the substrate of MEMS oscillator 10 and/orcompensation circuitry 18. As discussed in more detail below, thetemperature sensors may be integrated into the substrate of MEMSoscillator 10 and/or the substrate of compensation circuitry 18 (inthose instances where MEMS oscillator 10 and compensation circuitry 18are located on or in discrete substrates) to sense, sample and/or detectthe temperature of various, significant and/or critical portions of MEMSresonator 12 and/or compensation circuitry 18. Alternatively, or inaddition to, temperature sensors may be discrete devices positionedand/or located above and/or below MEMS oscillator 10 and, in particular,MEMS resonator 12 (for example, as part of (or integrated into)compensation and control circuitry 16 in a hybrid integrated orflip-chip packaging configuration (see, FIGS. 17B and 17C,respectively), which is discussed below.

With reference to FIG. 9B, in another embodiment, compensation circuitry18 may also include frequency divider circuitry 42. This embodimentprovides the flexibility to provide a signal(s) having a wide range ofoutput frequencies after fabrication, test, and/or calibration and/orduring operation. In this regard, compensated MEMS 100 of FIG. 9B maygenerate or provide an output signal having a stable and precise higheror lower frequency than the frequency of the output of MEMS oscillator10. For example, in this embodiment, the present invention may beemployed to provide a highly controllable, programmable, definable,selectable and/or accurate output signal having a stable low frequency(for example, 1 Hz-1 MHz) or a stable moderate frequency (for example,1-1 GHz) or a higher frequency (for example, 1-10 GHz). That is, the“post” frequency divider circuitry 42 may be employed to divide orreduce a relatively high and stable frequency output by the frequencymultiplier circuitry 28 to relatively lower stable frequencies of, forexample, 1 Hz-10 MHz.

Notably, certain PLLs may output more precise/stable signals (forexample, a more precise/stable frequency, phase, jitter, duty cycle,locking/response time, noise rejection and/or noise immunity) at higherfrequencies (for example, 1-2 GHz) when compared to lower frequencies(for example, 10-50 MHz). As such, in this embodiment, the output offrequency multiplier circuitry 28 may be provided to frequency dividercircuitry 42 which divides the precise/stable signal(s) at the higherfrequencies (for example, 1-2 GHz) to a precise/stable signals havinglower frequencies (for example, 1 Hz-50 MHz). In this way, thecharacteristics of the output signal of compensation circuitry 18 may beenhanced and/or optimized for a particular application (afterfabrication, test, and/or calibration and/or during operation) bycontrolling, adjusting and/or programming frequency multiplier circuitry28 and/or frequency divider circuitry 42.

The frequency divider circuitry 42 may include one or more PLLs, DLLs,digital/frequency synthesizers and/or FLLs. The division may be in fineor coarse increments. The PLLs, DLLs and/or FLLs may be cascaded inseries so that a particular, precise, stable and/or selectable frequencyand phase are obtained. For example, compensation circuitry 18 mayinclude an integer or a fractional-N PLL (or a precisely controllableDLL, fine-fractional-N DLL or fractional-N DLL (hereinafter collectively“fractional-N DLL”)), or combinations thereof, to precisely select,control and/or set the output signal of compensated MEMS oscillator 100.In this regard, the output of MEMS oscillator 10 is provided to theinput of the fractional-N PLL or fractional-N DLL, which may be pre-set,pre-programmed and/or programmable to provide an output signal having aprecise and/or stable frequency that is lower than the output signal ofMEMS 10.

The parameters, references, values and/or, coefficients employed infrequency multiplier circuitry 28 may be provided by control circuitry22 (see, for example, FIGS. 9A and 9B) and/or externally or via memory20 (see, for example, FIG. 9C). These parameters, references, valuesand/or coefficients may be provided either before or during operation ofcompensated MEMS oscillator 100. In this regard, as mentioned above, auser/operator or external circuitry/devices/systems may provideinformation representative of the parameters, references, values and/orcoefficients, via data signal lines 34, to set, change, and/or programfrequency multiplier circuitry 28. Indeed, in all of the embodimentsdescribing and illustrating the present invention, the parameters,references (for example, frequency and/or phase), values and/orcoefficients may be provided directly to circuitry comprisingcompensation circuitry 18 in lieu of (or in addition to) controlcircuitry 22.

Notably, with reference to FIG. 9D, frequency multiplier circuitry 28may be configured to output a plurality of signals, each having desired,selected and/or predetermined characteristics (for example, frequencyand/or phase). In this embodiment, frequency/phase compensated MEMSoscillator 100 provides and/or generates a number of precise, stable andcontrollable output signals using the output of MEMS oscillator 10. Forexample, each output of frequency multiplier circuitry 28 may be apredetermined frequency (for example, 2.5 .times., 10 .times., 12.34.times. or 23.4567. times. the frequency of the output signal of MEMSoscillator 10) as well as a desired, selected and/or predetermined phaserelationship relative to the other output signals (for example, 0°, 45°,90° and/or 180°). Indeed, the frequency and/or phase relationship may beprogrammable (for example, via an operator, external device or controlcircuitry 22) during, for example, fabrication, test, and calibrationand/or during normal operation. Notably, the plurality of outputs may begenerated by the same or separate or different frequency multipliercircuitry 28.

With reference to FIGS. 10A and 10B, in another embodiment of thepresent invention, compensation circuitry 18 consists of frequencydivider circuitry 42. In this regard, compensation circuitry 18 dividesthe frequency of the output signal of MEMS oscillator 10 to a preciseand/or stable frequency that is lower than the frequency of the outputsignal of MEMS oscillator 10. As mentioned above, frequency dividercircuitry 42 may include one or more PLLs, DLLs, digital/frequencysynthesizers (for example, DDSs) and/or FLLs. The division may be infine or coarse increments. The PLLs, DLLs and/or FLLs may be cascaded inseries so that a particular, precise, stable and/or selectable frequencyand phase are obtained. The characteristics of the output signal ofcompensated MEMS 100 may be precise and/or stable over a short period oftime (for example, over 1-10 microseconds, 1-60 seconds or 1-10 minutes)or an extended period of time (for example, over 1-10 hours, 1-10 daysor a month).

With reference to FIG. 10C, in another embodiment, compensationcircuitry 18 may also include frequency multiplier circuitry 28. Similarto the embodiment of FIG. 9B, this embodiment provides the flexibilityto provide a signal(s) having a wide range of output frequencies afterfabrication, test, and/or calibration and/or during operation. In thisregard, compensated MEMS 100 of FIG. 10C may generate or provide anoutput signal having a stable and precise higher or lower frequency thanthe frequency of the output of MEMS oscillator 10. For example, in thisembodiment, the “post” frequency multiplier circuitry 28 may be employedto multiply or increase a relatively low and stable frequency output bythe frequency divider circuitry 42 to relatively high stable frequenciesof, for example, 1-50 GHz.

Indeed, certain circuitry that may be employed in frequency dividercircuitry 42 (for example, certain DLLs) may output more precise/stablesignals (for example, a more precise/stable frequency, phase, jitter,duty cycle, locking/response time, noise rejection and/or noiseimmunity) at higher frequencies (for example, 1-2 GHz) when compared tolower frequencies (for example, 1-50 MHz). As such, in one embodiment,the output of frequency divider circuitry 42 may be provided tofrequency multiplier circuitry 28 which multiplies the precise/stablesignal(s) at the lower frequencies (for example, 1-50 MHz) to aprecise/stable signals having higher frequencies (for example, 1-2 GHz).In this way, the characteristics of the output signal of compensationcircuitry 18 may be enhanced and/or optimized for a particularapplication (after fabrication, test, and/or calibration and/or duringoperation) by controlling, adjusting and/or programming frequencydivider circuitry 42 and/or frequency multiplier circuitry 28.

The frequency multiplier circuitry 28 may include one or more PLLs,DLLs, digital/frequency synthesizers (for example, DDS) and/or FLLs. Themultiplication may be in fine or coarse increments. The PLLs, DLLsand/or FLLs may be cascaded in series so that a particular, precise,stable and/or selectable frequency and phase are obtained. For example,compensation circuitry 18 may include an integer or a fractional-N PLLor fractional-N DLL, or combinations thereof, to precisely select,control and/or set the output signal of compensated MEMS oscillator 100.In this regard, the output of MEMS oscillator 10 is provided to theinput of the fractional-N PLL or fractional-N DLL, which may be pre-set,pre-programmed and/or programmable to provide an output signal having aprecise and/or stable frequency that is lower than the output signal ofMEMS 10.

The parameters, references (for example, frequency and/or phase), valuesand/or coefficients employed in frequency multiplier circuitry 28 may beprovided by control circuitry 22 (see, for example, FIGS. 9A and 9B)and/or externally or via memory 20 (see, for example, FIG. 9C). Theseparameters, references, values and/or coefficients may be providedeither before or during operation of compensated MEMS oscillator 100. Inthis regard, as mentioned above, a user/operator or externalcircuitry/devices/systems may provide information representative of theparameters, references, values and/or coefficients, via data signallines 34, to set, change, and/or program frequency multiplier circuitry28. Indeed, in all of the embodiments describing and illustrating thepresent invention, the parameters, references, values and/orcoefficients may be provided directly to circuitry comprisingcompensation circuitry 18 in lieu of (or in addition to) controlcircuitry 22.

Notably, with reference to FIG. 10D, frequency divider circuitry 42 maybe configured to output a plurality of signals, each having desired,selected and/or predetermined characteristics (for example, frequencyand/or phase). In this embodiment, frequency/phase compensated MEMSoscillator 100 provides and/or generates a number of precise, stable andcontrollable output signals using the output of MEMS oscillator 10. Forexample, each output of frequency divider circuitry 42 may be apredetermined frequency (for example, 1 .times., 0.5 .times., 0.25.times. or 0.23456 .times. the frequency of the output signal of MEMSoscillator 10) as well as a desired, selected and/or predetermined phaserelationship relative to the other output signals (for example, 0.degree., 45 .degree., 90 .degree. and/or 180 .degree.). Indeed, thefrequency and/or phase relationship may be programmable (for example,via an operator, external device or control circuitry 22) during, forexample, fabrication, test, and calibration and/or during normaloperation. Notably, the plurality of outputs may be generated by thesame or separate or different frequency divider circuitry 42.

The parameters, references (for example, frequency and/or phase), valuesand/or coefficients employed in frequency divider circuitry 42 (andfrequency multiplier circuitry 28) may be provided by control circuitry22 (see, for example, FIG. 10A) and/or externally or via memory 20 (see,for example, FIG. 10B). These parameters, references, values and/orcoefficients may be provided either before (for example, fabrication,test, and/or calibration) or during operation of compensated MEMSoscillator 100.

As mentioned above, compensated MEMS oscillator 100 may provide and/orgenerate a plurality of output signals each having a programmable,precise, stable and/or selectable frequency and/or phase. With referenceto FIGS. 11A, 11B, 12A and 12B, in several embodiments, frequencydivider circuitry 42 may include one or more PLLs, DLLs,digital/frequency synthesizers (for example, DDSs) and/or FLLs. Forexample, where frequency divider circuitry 42 employs a DLL, each outputsignal may be one of the delay points between adjustable delay elementsthereby providing a plurality of output signals each having the same (orsubstantially the same) frequency but a different phase relative to theother output signals.

Further, frequency divider circuitry 42 may be comprised of a pluralityof PLLs, DLLs, digital/frequency synthesizers and/or FLLs. In thisregard, the PLLs, DLLs, digital/frequency synthesizers and/or FLLs maybe configured in parallel to receive the output of MEMS oscillator 10and to generate and provide a plurality of output signals each having aprogrammable, precise, stable and/or selectable frequency and/or phase.The particular frequency and/or phase of each output signal may beprogrammed, set and/or determined by the parameters, references (forexample, frequency and/or phase), values and/or coefficients appliedand/or employed by frequency divider circuitry 42. For example, in thoseinstances where a plurality of fractional-N PLLs are employed, theparameters, references, values and/or coefficients (for example, data ofthe integer value for the main and auxiliary divider circuitry and/orthe values for the fractional-N divider circuitry) provided to and/orprogrammed into each fractional-N PLL determines the frequency of thecorresponding output signal.

As mentioned above, compensated MEMS oscillator 100 of the presentinvention may include a plurality of programmable output signals. Withreference to FIGS. 13A and 13B, compensated MEMS oscillator 100, in oneembodiment, may include compensation circuitry 18 having a plurality offrequency multiplier circuitry 28 connected to a plurality of frequencydivider circuitry 42, wherein each frequency divider circuitry 42 isassociated with one frequency multiplier circuitry 28. In thisembodiment, each output signal of compensated MEMS oscillator 100 mayhave independent characteristics (for example, an independent frequencyand/or independent phase) relative to the other output signals.

With reference to FIGS. 14A and 14B, in other embodiments, compensatedMEMS oscillator 100 may include frequency multiplier circuitry 28 (FIG.14A) or frequency divider circuitry 42 (FIG. 14B) coupled to a pluralityof secondary frequency multiplier/divider circuitry 44. In thisembodiment, each output signal of compensated MEMS oscillator 100 mayhave programmable characteristics (for example, a programmable frequencyand/or a programmable phase) thereby providing a flexible MEMSoscillator device having a plurality of programmable output signals.

For example, in these embodiments, frequency multiplier circuitry 28(FIG. 14A) and frequency divider circuitry 42 (FIG. 14B) may generate astable, precise output signal having a predetermined frequency and/orphase. The secondary frequency multiplier/divider circuitry 44, eachhaving different parameters, references, values and/or coefficients, maybe programmed, predetermined and/or preset (for example, duringfabrication, test, calibration and/or dynamically during operation) toprovide an output signal having a predetermined frequency and/or phasethat is different from the frequency and/or phase of the output offrequency multiplier circuitry 28 (FIG. 14A) or frequency dividercircuitry 42 (FIG. 14B).

With reference to FIGS. 14C and 14D, in another embodiment, compensatedMEMS oscillator 100 may include frequency multiplier circuitry 28 (FIG.14C) or frequency divider circuitry 42 (FIG. 14D) coupled to secondaryfrequency multiplier/divider circuitry 44. Similar to the embodiments ofFIGS. 14A and 14B, in these embodiments, the output signal of MEMSoscillator 10 is provided to frequency multiplier circuitry 28 (FIG.14C) or frequency divider circuitry 42 (FIG. 14D) to generate a stable,precise output signal having a predetermined frequency and/or phase. Thefrequency multiplier circuitry 28 and frequency divider circuitry 42 ofFIGS. 14C and 14D, respectively, may include circuitry that responds“slowly” to changes in parameters, references, values and/orcoefficients. The secondary frequency multiplier/divider circuitry 44may include circuitry that responds “rapidly” to such changes. In thisway, compensated MEMS 100 of FIGS. 14C and 14D may be employed toprovide a stable and precise output signal having a frequency and/orphase that may be rapidly modified.

For example, frequency multiplier circuitry 28 (FIG. 14C) and frequencydivider circuitry 42 (FIG. 14D) may provide an output signal having afirst frequency (for example, 1 MHz). The secondary frequencymultiplier/divider circuitry 44 may be rapidly and dynamicallyprogrammed and/or re-programmed to provide an output signal havingsecond frequencies (for example, 8 MHz, 9 MHz and/or 10 MHz).

Notably, in one embodiment, frequency multiplier circuitry 28 (FIG. 14C)and frequency divider circuitry 42 (FIG. 14D) may be a fractional-N PLLor fractional-N DLL which may be “slow” to respond to changes inparameters, references, values and/or coefficients. However, secondaryfrequency multiplier/divider circuitry 44 may be an integer type PLL orDLL which may respond quickly to changes in parameters, references,values and/or coefficients. As such, the frequency of the output signalof frequency multiplier circuitry 28 (FIG. 14C) and frequency dividercircuitry 42 (FIG. 14D) may be a base frequency which is employed bysecondary frequency multiplier/divider circuitry 44 to generate anoutput that responds rapidly to dynamic programming and/orre-programming and is an integer multiple of the base frequency. In thisregard, the granularity of frequency of the output signal of compensatedMEMS 100 depends on the base frequency.

For example, where the base frequency is 200 kHz and secondary frequencymultiplier/divider circuitry 44 is an integer type PLL or DLL, thefrequency of the output signal of compensated MEMS 100 may be, forexample, 10 MHz (i.e., multiplication factor is 50), 10.2 MHz (i.e.,multiplication factor is 51), 10.4 MHz (i.e., multiplication factor is52) or 10.6 MHz (i.e., multiplication factor is 53). Notably, thediscussions pertaining to FIGS. 14C and 14D are also applicable to FIGS.14A and 14B. For the sake of brevity, those discussions will not berepeated.

Notably, any and all of the techniques and/or configurations describedherein for supplying or providing the parameters, references, valuesand/or coefficients to, as well as controlling, programming and/oradjusting the performance of compensation circuitry 18 may beimplemented in the embodiments/inventions of FIGS. 11A, 11B, 12A, 12B,13A, 13B, 14A and 14B. For the sake of brevity, those discussions willnot be repeated.

The compensated MEMS oscillator 100 of the present invention may bepackaged/fabricated using a variety of techniques, including, forexample, monolithically (see, for example, FIGS. 15A-15F), multi-chip(see, for example, FIGS. 16A-16C and 17A), hybrid integrated (see, forexample, FIG. 17B), and/or flip-chip (see, for example, FIG. 17C).Indeed, any fabrication and/or packaging techniques may be employed,whether now known or later developed. As such, all such fabricationand/or packaging techniques are intended to fall within the scope of thepresent invention.

In particular, with reference to FIGS. 15A-15F, MEMS resonator 12 anddrive circuitry 14 may be integrated on substrate 46 as compensation andcontrol circuitry 16. Any fabrication technique and/or process may beimplemented. For example, the systems, devices and/or techniquesdescribed and illustrated in the following non-provisional patentapplications may be implemented (see, for example, FIGS. 18A-18H):

(1) “Electromechanical System having a Controlled Atmosphere, and Methodof Fabricating Same”, which was filed on Mar. 20, 2003 and assigned Ser.No. 10/392,528;

(2) “Microelectromechanical Systems, and Method of Encapsulating andFabricating Same”, which was filed on Jun. 4, 2003 and assigned Ser. No.10/454,867;

(3) “Microelectromechanical Systems Having Trench Isolated Contacts, andMethods of Fabricating Same”, which was filed on Jun. 4, 2003 andassigned Ser. No. 10/455,555;

(4) “Anchors for Microelectromechanical Systems Having an SOI Substrate,and Method for Fabricating Same”, which was filed on Jul. 25, 2003 andassigned Ser. No. 10/627,237; and

(5) “Anti-Stiction Technique for Thin Film and Wafer-Bonded EncapsulatedMicroelectromechanical Systems”, which was filed on Oct. 31, 2003 andassigned Ser. No. 10/698,258.

The inventions described and illustrated in the aforementioned patentapplications may be employed to fabricate compensated MEMS oscillator100 of the present inventions. For the sake of brevity, thosediscussions will not be repeated. It is expressly noted, however, thatthe entire contents of the aforementioned patent applications,including, for example, the features, attributes, alternatives,materials, techniques and advantages of all of the inventions, areincorporated by reference herein.

With reference to FIGS. 15B and 15F, temperature sensors 48 (which weregenerally identified as 26, for example, in the block diagram of FIGS.2E, 1A, 14A and 14B) may be disposed and/or located at selected,significant and/or “critical” locations on the substrate of MEMSoscillator 10 and/or compensation and control circuitry 16 to providecontrol circuitry 22 and/or temperature sensor circuitry 24 withtemperature information that may be significant to determine orcalculate parameters, references, values and/or coefficients forcompensation circuitry 18. The temperature sensors 48 may be, forexample, diodes, transistors, resistors or varistors, and/or one or moreMEMS structures which are disposed and/or located on or in the substrateof MEMS oscillator 10 and/or compensation and control circuitry 16. Thetemperature sensors may be integrated into MEMS oscillator 10 to sense,sample and/or detect the temperature of various, significant and/orcritical portions of MEMS resonator 12 and/or compensation circuitry 18.Alternatively, or in addition to, temperature sensors may be discretedevices positioned and/or located above and/or below MEMS resonator 12and/or compensation circuitry 18.

With continued reference to FIGS. 15B and 15F, temperature sensors 48may be metal resistors (for example, platinum) disposed on the surfaceof substrate 46. In addition, or in lieu of, temperature sensors 48 maybe implanted within substrate 46.

Notably, the data provided by temperature sensors 48 may be in a voltageor current that is in analog or digital form. That data may be, asdescribed above, provided to temperature sensor circuitry 24, or moredirectly to control circuitry 22 for processing and analysis. Indeed,the data may be provided directly to compensation circuitry 18 forimmediate processing, adjustment and/or control of the operation ofcompensation circuitry 18.

With reference to FIGS. 17A and 17B, in those instances where MEMSoscillator 10 and compensation and control circuitry 16 are fabricatedon separate substrates, the various signals may be provided using wireinterconnects 50 electrically interconnecting bond pads located onsubstrates 46 a and 46 b. Alternatively, a flip-chip configuration maybe implemented. See, for example, FIG. 17C). As mentioned above, allpackaging and interconnection technique, whether now known or laterdeveloped, are intended to fall within the scope of the presentinvention.

As mentioned above, MEMS oscillator 10 may be temperature compensated oruncompensated. The characteristics of the output signal of MEMSoscillator 10 (for example, frequency, amplitude and/or sensitivities)may be determined, measured, tested and/or analyzed before and/or afterpackaging. In this way, a reference of the output signal of MEMSoscillator 10 is determined and employed to calculate the parameters,references, values and/or coefficients for compensation and controlcircuitry 16 (for example, parameters and/or coefficients for thefractional-N PLL). Using the reference characteristics of the outputsignal of MEMS oscillator 10 facilitates adjustment, correction and/orcontrol of the frequency and/or phase of output signal 30 ofcompensation circuitry 18. For example, where a fractional-N PLL isemployed, control circuitry 22 may provide the data of the integer valuefor the main and auxiliary divider circuitry 42 and/or the values forthe fractional-N divider circuitry to frequency multiplier circuitry 28via data/control signal lines 32. Accordingly, the output signal(s) onsignal line 30, after proper adjustment, correction and control, possesssuitable, desired, predetermined attributes and/or characteristics (forexample, frequency, phase, jitter, duty cycle, response time, and/ornoise immunity).

The calibration of MEMS oscillator 10 may be completed before and/orafter packaging. The calibration may be at one operating condition (forexample, one temperature) or at multiple operating conditions. Indeed,the calibration may consist of fixing the frequency and temperaturecompensation (if any). Notably, however, in certain embodiments, nocalibration is performed and any adjustment to the characteristics ofthe output signal of compensated MEMS 100 (due to the absence ofcalibration) may be addressed by compensation and control circuitry 16.In this embodiment, it may be advantageous to provide a range ofprogrammability to account or compensate for eliminating and/or omittingtypical calibration processes/techniques. For example, it may beadvantageous to employ topologies or embodiments of compensation andcontrol circuitry 16 that provide significant programmability in theevent that the frequency of the output of MEMS 10 (for example, theinitial frequency) varies significantly.

There are many inventions described and illustrated herein. Whilecertain embodiments, features, materials, configurations, attributes andadvantages of the inventions have been described and illustrated, itshould be understood that many other, as well as different and/orsimilar embodiments, features, materials, configurations, attributes,structures and advantages of the present inventions that are apparentfrom the description, illustration and claims. As such, the embodiments,features, materials, configurations, attributes, structures andadvantages of the inventions described and illustrated herein are notexhaustive and it should be understood that such other, similar, as wellas different, embodiments, features, materials, configurations,attributes, structures and advantages of the present inventions arewithin the scope of the present invention.

For example, while many of the exemplary embodiments mentionimplementing PLLs, DLLs, digital/frequency synthesizers and/or FLLs,other suitable clock alignment circuitry may be employed. In thisregard, compensation circuitry 18 may employ an RC, RCL,ring-oscillator, and/or frequency modulation synthesizer. Indeed, anyclock or signal alignment circuitry, whether now known or laterdeveloped, may be employed to generate an output signal having preciseand stable characteristics (for example, frequency and/or phase).

Similarly, frequency multiplier circuitry 28, frequency dividercircuitry 42 and secondary frequency multiplier/divider circuitry 44 maybe implemented using any clock or signal alignment circuitry describedherein, for example, PLLs, DLLs, digital/frequency synthesizers (forexample, DDS) and/or FLLs, as well as any combinations and permutationsthereof (see, for example, FIGS. 23A-23C). Indeed, any permutationand/or combination of such clock or signal alignment circuitry may beemployed for the topologies of compensation circuitry 18 (see, forexample, FIGS. 23B, 23C and 24A-24I). Moreover, frequency multipliercircuitry 28, frequency divider circuitry 42, and secondary frequencymultiplier/divider circuitry 44 may be comprised of and/or implementedusing digital and/or analog circuitry.

The permutations and/or combinations of the clock or signal alignmentcircuitry may include circuitry for providing pre-compensation,intermediate or post-compensation of the signal before providing anoutput signal having desired and/or predetermined characteristics. Suchpre-compensation, intermediate or post-compensation may be employed tooptimize and/or enhance the characteristics of the signal relative toother circuitry in, for example, frequency multiplier circuitry 28,frequency divider circuitry 42, and secondary frequencymultiplier/divider circuitry 44 and/or to enhance and/or optimize theoverall system signal quality or characteristics (for example, phasenoise). For example, frequency multiplier circuitry 28 may be comprisedof pre-compensation circuitry that receives the output of MEMSoscillator 10, reduces the frequency and provides an output to othercircuitry that multiplies the frequency of that output to anotherfrequency that is higher than the frequency of the output of MEMSoscillator 10. (See, for example, FIG. 23A). Similarly, frequencydivider circuitry 42 may be comprised of pre-compensation circuitry thatreceives the output of MEMS oscillator 10 and increases the frequency ofthe output signal of MEMS oscillator 10 before dividing the frequency toanother frequency that is lower than the frequency of the output of MEMSoscillator 10. (See, for example, FIG. 23C).

In addition, it should be noted that while clock or signal alignmentcircuitry may on average adjust, compensate, control, program, and/ordefine in a particular manner, for example, increase/multiply orreduce/divide the frequency of an input signal, such circuitry may, atcertain moments or periods, increase/multiply the frequency and at othermoments or periods reduce/divide the frequency (for example, as theoperating temperature of the system 100 varies). Accordingly, while onaverage frequency divider circuitry 42 reduces/divides the frequency ofan input signal, at certain moments or periods, frequency dividercircuitry 42 may actually increase/multiply the frequency in order toprovide appropriate output signal characteristics.

Moreover, as mentioned above, compensated MEMS oscillator 100 may befully integrated or partially integrated. (See, for example, FIGS.15A-17C). Indeed, each of the elements and/or circuitry of MEMS 10 andcompensation and control circuitry 16 may be discrete components, forexample, discrete drive circuits, MEMS resonators, loop filtercapacitors and/or resistors.

For example, although drive circuitry 14 has been illustrated asintegrated with MEMS resonator 12 on substrate 46 a, drive circuitry 14may be disposed or integrated on substrate 46 b. With reference to FIGS.19A-19D, drive circuitry 14 is integrated on substrate 46 b withcompensation and control circuitry 16. In this way, the fabrication ofcompensated MEMS oscillator 100 may be more efficient and less costlythan those embodiments where drive circuitry 14 is disposed on the samesubstrate as MEMS resonator 12.

Indeed, with reference to FIG. 20, drive circuitry 14 may be fabricatedon a substrate that is different than MEMS resonator 12 and compensationand control circuitry 16. Notably, temperature sensors 48 may beincorporated and/or employed in these embodiments using any manner orconfiguration as described herein (See, for example, the alternativeconfigurations, layouts and/or topologies of FIGS. 19A-19D).

Further, while the exemplary embodiments and/or techniques of theinventions have been described with a certain configuration. Forexample, in certain illustrations, temperature sensor circuitry 24receives data (which is representative of the ambient temperature of orin a given location) from MEMS oscillator 10. The temperature sensorcircuitry 24 may also receive data from compensation and controlcircuitry 16 in lieu of, or in addition to the temperature “data”received from MEMS oscillator 10. (See, FIGS. 21A and 21B). In thisregard, the output signal of MEMS oscillator 100 may be compensated forthe affects, modifications, changes and/or variations in the operatingperformance and/or characteristics of compensation and control circuitry16 due to temperature changes.

Notably, it may be advantageous to design MEMS oscillator 10 to have aninverse temperature coefficient relationship to that of compensationcircuitry 18. In this way, any impact on the characteristics of theoutput signal of MEMS 10 and the adjustment, correction, and/or controlintroduced by compensation circuitry 18 that is caused or due to changesin the operating temperature(s) may be minimized, reduced, canceledand/or offset.

In addition, although control circuitry 22 has been described andillustrated as being resident on or in the substrate containingcompensation and control circuitry 16, control circuitry 22 may beremote, discrete and/or separate therefrom. In this regard, temperaturecompensation calculations may be performed by a remote and/or discretegeneral-purpose processor (which may have different or several primaryor main functions and/or purposes) and provided to frequency/phasecompensated MEMS 100. In this way, the general-purpose processor mayperform its primary tasks, functions and/or purposes and, for example,periodically (for example, every 1/10 of a second) or intermittentlyre-calculate new, suitable, optimum and/or enhanced parameters,references, values and/or coefficients employed by compensationcircuitry 18 in order to generate and/or provide an adjusted, correctedand/or controlled output having, for example, a desired, selected and/orpredetermined frequency and/or phase. As such, compensated MEMSoscillator 100 may include less circuitry on the substrate (and morelikely consumes lower power) but still compensates for temperaturechanges (which are often slow).

Notably, control circuitry 22 may be comprised of and/or implementedusing digital and/or analog circuitry.

Further, temperature sensor circuitry 24 may also be discrete, remoteand/or separate from frequency/phase compensated MEMS 100. Thetemperature circuitry 24 may be comprised of and/or implemented usingdigital and/or analog circuitry. In one embodiment, temperature sensors48 may be integrated into or a part of temperature sensor circuitry 24.In this regard, the temperature sensors 48 are integrated into thecircuits and/or circuitry of temperature circuitry 24.

As mentioned above, MEMS oscillator 10 may be partially temperaturecompensated (see, for example, FIG. 5A) or fully temperaturecompensated, or includes little to no temperature compensation (see, forexample, FIGS. 4A and 6A).

In addition, MEMS resonator 12 and/or drive circuit 14 may employ anytype of MEMS design and/or control, whether now known or laterdeveloped, including those discussed above in the Background of theInvention. For example, the MEMS resonator and/or drive circuit mayinclude any of the designs and/or control techniques that are describedand illustrated in the following non-provisional patent applications:

(1) “Temperature Compensation for Silicon MEMS”, which was filed on Apr.16, 2003 and assigned Ser. No. 10/414,793; and

(2) “Frequency Compensated Oscillator Design for Process Tolerances”,which was filed on Oct. 3, 2003 and assigned Ser. No. 10/679,115.

The inventions described and illustrated in the aforementioned patentapplications may be employed to design, control and/or fabricate MEMSresonator 12 and/or drive circuit 14 of the present inventions. For thesake of brevity, those discussions will not be repeated. It is expresslynoted, however, that the entire contents of the aforementioned patentapplications, including, for example, the features, attributes,alternatives, materials, techniques and advantages of all of theinventions, are incorporated by reference herein.

Further, each substrate or chip may include one or more MEMS resonatorsand/or MEMS oscillator. In this way, the compensated MEMS oscillator mayinclude a plurality of oscillators 100 on the substrate/chip wherein afirst compensated MEMS oscillator 100 a may provide a first outputsignal having a first set of characteristics and a second compensatedMEMS oscillator 100 b may provide a second output signal having a secondset of characteristics. The first output signal may be a low frequencyoutput signal generated by low power consumption circuitry and thesecond output signal may be a high frequency output signal generated byhigh power consumption circuitry. Thus, in one embodiment, the lowfrequency signal may run continuously and the high frequency signal maybe intermittently used and turned on as needed. As such, in one aspect,this embodiment provides a technique for managing power consumption of acompensated MEMS oscillator according to the present invention.

In another technique to manage power consumption, frequency dividercircuitry 42 may be programmable that provides an output signal of thecompensated MEMS 100 frequency having, for example, a low frequency, forexample, 1-100 Hz to maintain accurate time keeping (see, for example,FIGS. 10A and 10B). The frequency divider circuitry 42 may include lowpower circuitry having, for example, a fractional-N divider stage. Inthis way, the power consumption of compensated MEMS 100 (and, inparticular, frequency divider circuitry 42) is consistent with and/ortailored to a given application (for example, time keeping applicationswhich often require low power because power is provided by batteries).Other circuitry-power consumption topologies and/or configurations arecontemplated, and, as such, all circuitry-power consumption topologiesand/or configurations, whether now known or later developed, areintended to be within the scope of the present invention.

Notably, as mentioned above, the output signal of compensated MEMSoscillator 100 may be single ended or double ended (i.e., differentialsignaling). The “shape” of the output signal (for example, square,pulse, sinusoidal or clipped sinusoidal) may be predetermined and/orprogrammable. In this regard, information which is representative of the“shape” of the output signal may be stored or programmed in memory 20during fabrication, test, calibration and/or operation. In this way,control circuitry 22 and/or compensation circuitry 18 may access memory20 to such information during start-up/power-up, initialization,re-initialization and/or during normal operation of compensationcircuitry 18.

In addition, or in lieu thereof, a user/operator or externalcircuitry/devices/systems (as mentioned above) may provide informationwhich is representative of the “shape” of the output signal, via datasignal lines 34, to set, change, enhance and/or optimize thecharacteristics of the output signal(s) on signal line 30. Suchinformation may be provided directly to control circuitry 22, memory 20and/or compensation circuitry 18.

Indeed, control circuitry 22 may introduce slight frequency variationsas a function of an external command or analog signal. For example, sucha configuration may simulate a voltage-controlled oscillator. Notably,any introduction of frequency variations as a function of an externalcommand or analog signal may be incorporated into the compensationcircuitry 18 (for example, frequency multiplier circuitry 28 orimpressed onto the MEMS resonator 12).

The present invention may be implemented in, for example, computers,telephones, radios, GPS systems, and the like. The compensation andcontrol functions of the present invention, among others, include: (1)compensation of “initial” frequency and/or phase errors, (2)compensation for temperature changes, (3) compensation of aging andother debilitating effects with data from external sources (for example,from cell phone base station data), (4) variation for externalrequirements like Doppler shift, and/or (5) modulation or spreading ofthe output signal. Indeed, the present invention may be used inessentially any application where a crystal oscillator is employed.

For example, in one embodiment, the present invention(s) may be employedin conjunction with modulation circuitry 52. In this regard, in thoseembodiments where the frequency and/or phase of the output signal may bechanged, modified and/or altered dynamically during operation, thatchange, modification and/or alteration may represent information/data.With reference to FIGS. 22A and 22B, a data stream (i.e., input datastream) may be transmitted and/or encoded, using modulation circuitry52, by altering the frequency and/or phase of the output signal ofcompensation and control circuitry 16.

It should be noted that the present invention(s) may be employed in thecontext of PSK, FSK, QAM and QPSK signaling techniques, as well asmodulation formats that encode fewer or more bits per transmittedsymbol. Moreover, other communications mechanisms that use encodingtables or use other modulation mechanisms may also be used, for example,PAM-n (where n=2 to 16, for example), CAP, and wavelet modulation. Inthis regard, the techniques described herein are applicable to allmodulation schemes, whether now known or later developed, including butnot limited to, PSK, FSK, QAM and QPSK encoding; and, as such, areintended to be within the scope of the present invention.

It should be further noted that the term “circuit” may mean, among otherthings, a single component or a multiplicity of components (whether inintegrated circuit form or otherwise), which are active and/or passive,and which are coupled together to provide or perform a desired function.The term “circuitry” may mean, among other things, a circuit (whetherintegrated or otherwise), a group of such circuits, a processor(s), astate machine, a group of state machines, software, a processor(s)implementing software, or a combination of a circuit (whether integratedor otherwise), a group of such circuits, a state machine, group of statemachines, software, a processor(s) and/or a processor(s) implementingsoftware, processor(s) and circuit(s), and/or processor(s) andcircuit(s) implementing software.

The term “data” may mean, among other things, a current or voltagesignal(s) whether in an analog or a digital form. The term “measure”means, among other things, sample, sense, inspect, detect, monitorand/or capture. The phrase “to measure” or similar, means, for example,to sample, to sense, to inspect, to detect, to monitor and/or tocapture. The term “program” may mean, among other things, instructions,parameters, variables, software, firmware, microcode and/or configurablehardware conformation (for example, code stored in memory 20).

In the claims, the term “set of values”, “values” or the like (forexample, subset of values), means, among other things, parameters,references (for example, frequency and/or phase), values and/orcoefficients, or the like.

1. A system for generating a timing signal comprising: amicroelectromechanical system (MEMS) resonator; drive circuitry coupledto the MEMS resonator and configured to drive the MEMS resonator with adrive signal to generate a reference signal having a first frequency; amemory device storing compensation data; control circuitry coupled tothe memory device and configured to generate a set of values based onthe compensation data and one or more operating temperature readings;and frequency adjustment circuitry coupled to the control circuitry andconfigured to: receive the reference signal generated by the MEMSresonator, receive the set of values generated by the control circuitry,and based on the reference signal and the set of values, generate atiming signal having a second frequency that is different from the firstfrequency.
 2. The system of claim 1, further comprising temperaturecompensation circuitry coupled to the control circuitry and the MEMSresonator and configured to provide the one or more operatingtemperature readings to the control circuitry.
 3. The system of claim 1,wherein the control circuitry is further configured to: access thememory device to retrieve the compensation data; and generate the set ofvalues based on the retrieved compensation data.
 4. The system of claim1, wherein the compensation data comprises a look-up table relating thefirst frequency to an operating temperature of the MEMS resonator. 5.The system of claim 4, wherein the set of values is generated based ondata in the look-up table.
 6. The system of claim 1, wherein the memorydevice comprises read-only memory or random-access memory.
 7. The systemof claim 1, wherein the control circuitry, the frequency adjustmentcircuitry, the temperature compensation circuitry, and the memory devicereside within a single chip.
 8. The system of claim 1, wherein the firstfrequency depends on an operating temperature of the MEMS resonator. 9.The system of claim 1, wherein the set of values is generated based onempirical data or a mathematical relationship.
 10. The system of claim1, wherein the compensation data is stored or programmed in the memorydevice during testing of the MEMS resonator, calibration of the MEMSresonator, or operation of the MEMS resonator.
 11. The system of claim1, wherein the frequency adjustment circuitry comprises a fractional-Nsynthesizer.
 12. The system of claim 11, wherein the fractional-Nsynthesizer comprises a charge pump, a phase detector, a loop filter, avoltage controlled oscillator (VCO), and a divider.
 13. The system ofclaim 12, wherein the phase detector comprises a phase-frequencydetector.
 14. The system of claim 13, wherein the loop filter comprisesan RC circuit.
 15. The system of claim 14, wherein the VCO comprises awideband VCO.
 16. The system of claim 15, wherein the divider isprogrammable.
 17. The system of claim 1, wherein the control circuitryis further configured to adjust the drive signal driving the MEMSresonator.
 18. The system of claim 17, wherein the control circuitryadjusts the drive signal according to changes in operating conditions orenvironment of the MEMS resonator.
 19. The system of claim 17, whereinthe control circuitry adjusts the drive signal based on the referencesignal and the one or more operating temperature readings.
 20. Thesystem of claim 1, wherein the second frequency is greater than thefirst frequency.
 21. The system of claim 1, wherein the second frequencyis less than the first frequency.
 22. A system for generating a timingsignal comprising: a microelectromechanical system (MEMS) resonator;drive circuitry coupled to the MEMS resonator and configured to drivethe MEMS resonator with a drive signal to generate a reference signalhaving a first frequency; a memory device storing compensation data;control circuitry coupled to the memory device and configured togenerate a set of values based on the compensation data and one or moreoperating temperature readings; temperature compensation circuitrycoupled to the control circuitry and the MEMS resonator and configuredto provide the one or more operating temperature readings to the controlcircuitry; and a fractional-N synthesizer comprising a charge pump, aphase detector, a loop filter, a voltage controlled oscillator, and adivider, wherein the factional-N synthesizer is coupled to the controlcircuitry and configured to: receive the reference signal generated bythe MEMS resonator, receive the set of values generated by the controlcircuitry, and based on the reference signal and the set of values,generate a timing signal having a second frequency that is differentfrom the first frequency.
 23. The system of claim 22, wherein the secondfrequency is greater than the first frequency.
 24. The system of claim22, wherein the second frequency is less than the first frequency.